bliffle

When I rev to 6000 I'm getting a driveline vibration. Maybe it's the transmission input shaft bearing, but maybe it's just the transmission mount, which several people have reported before.

Is there an easy way to determine which it is?

gsl-se addict

iTrader: (3)

Check this out if you haven't already:

http://www.mazdatrix.com/g2.htm

Also, is this just revving in neutral, or crusing at 6000 rpm, or both?

bliffle

I've gotta examine this more closely: record noises at idle, with clutch depressed, revving up tp 6000, etc. For the moment I'm going to hypothesize a bad transmission mount, which I thought might be easy but may be more than I thought.

83RxV6

another thing you can check is the universal joints a lot of times its as simple as that lift the back of the car up and block or chock the front wheels so the car doesnt move keep the car in gear and where the driveline mounts to the tranny and the rearend move the driveline in a virtical and horizontal direction to see if there is any movement chances are if there is a vibration especcially on deceleration ths is where youll find the problem

trochoid

iTrader: (6)

If this is happening in neutral, you can eliminate the driveshaft, it's not turning, neither is the tranny outout shaft. that leaves mounts, pilot bearing and input shaft bearing, all assuming this is in neutral, clutch out.

bliffle

I'm going to replace the transmission mount, then probably the ujoints (car has 160k) and maybe rearwheel bearings (while looking at brake pads). It's about time. It needs a new PB, too, methinks, but I'll wait for awhile.

bliffle

Can the transmission mount be replaced without removing the transmission? Is the mount on a subassembly cross brace or something to make this easy.

trochoid

iTrader: (6)

Break the cross member bolts loose, then use the factory jack under the tranny to unload the mount and remove the entire cross member.

stilettoman

iTrader: (1)

I would not replace anything until you remove and check the driveshaft. Just unbolt it at the back and pull it out. Then move the joints through their full movement by hand. They should move very freely. If there is any binding, that could cause the vibration. I have experienced this on 1st gen RX-7s several times in the past 15 years, and the driveshaft has always cured it for me. Can't help wondering how much more it would have cost to build these cars with grease fittings in the U-joints.

bliffle

Yeah, I remember squirting grease into the Ujoint nipples back in the 50s when I worked at a 2 pump station. 19 cents a gallon for regular.

But this doesn't seem like ujoints because it goes with engine speed, not wheel speed. But I'll replace the ujoints (or the whole driveshaft) pretty soon anyhow.

Jeff20B

iTrader: (13)

Is this your GSL-SE? Could be related to your sudden loss of coolant.

trochoid

iTrader: (6)

Good point Jeff. If it's the same car, and it is a seal, the higher the rpm, the greater the coolant loss and less lube on that housing. It could then be sort of a drag chatter that's causing the vibration.

83RxV6

damn Scott you and Jeff did come up with a good point i never would have thaught about it like that guess thats why you are the masters Im almost wondering if that may be what im hearing out of my car cause its chattered like that for about 2 months now it amost sounds like a broken flywheel chatter but if thats the case with the housing i would think i would have destroyed the motor by now

trochoid

iTrader: (6)

Friction chatter might be a more appropriate term instead of drag chatter.

bliffle

It's the same car!

I noticed the chatter a few days before the coolant loss.

So what're you saying? That a bad coolant seal allowed coolant to erode the lube at the rear engine bearing (gasp!)? And now it's spun the bearing?

bliffle

If it's a bad engine bearing shouldn't I have some secondary symptoms, like oilloss or oil dilution?

bliffle

I examined things closely and the water puddle is under the right front of the radiator, suggesting a radiator seam leak. I'm going to pull the radiator in a few days and have a radiator shop check/repair it. No signs of water or any other leaks in the engine compartment. Radiator seams are soft-soldered AFAIK and vibration can cause them to fail. Especially on a cheap aftermarket rad from radiators.com!

I still think the driveline vibration is a bad engine or transmission mount. They catch a lot of stray oil and after 23 years can be rotten.

I don't think those problems are related any more than that my electric door remote stopped working the same week. Perhaps what ties the rad to the doorlocks is that they were both done by my inept mechanic "R".

trochoid

iTrader: (6)

Wasn't refering to the bearings, but the interface between the apex seals and the housing surface. The mop provides lube at that interface, an inner coolant seal failure can wash it away. I tore an SE egine down that had blown seals front and rear, the engine looked like it had just been rebuilt or steamed cleaned internally.

bliffle

But if I had coolant in the combustion chamber I'd have white tailpipe smoke, and I don't.

trochoid

iTrader: (6)

Yep.